1. Field of the Invention
The present invention relates to the field of portable devices, and more particularly, to a method and a system for saving power of a portable device using both a mobile communication network and a fixed telephone network.
2. Description of the Related Art
Portable devices have rapidly developed from their operation using simple functions such as voice call and short message, to more complex functions, such as video telephony, e-book function, and Internet function. Recently, portable devices have been equipped with digital camera functions that capture both still and moving images. Accordingly, the portable device can easily photograph desired moving pictures or still images that may be stored and displayed at a latter time. In addition, the still or moving images may be provided to other users using an image transmission function. However, a communication which is considered to be most familiar with the general public in the daily life may be a regular landline phone using a fixed telephone network. The landline phones have also been developed to provide, a cordless phone function, wherein the handset may be wirelessly connected to a residential base station. Additionally, the cordless phone function is used for business use, for example, representatively, a Digital European Cordless Telephone (DECT) system. The DECT system is selected as European Standards by European Standards Organization, i.e., European Telecommunications Standards Institute (ETSI). Portable devices which can use the mobile communication network and the fixed telephone network have been developed, respectively. Recently, such portable devices may operate as a complex cordless device that can use both the mobile communication network and the fixed telephone network. However, in case of the complex cordless device, it is disadvantageous in that the standby mode for mobile communication network and fixed telephone network requires large power consumption.